1. Field of the Invention
The present invention is directed to a system for delivering liquid to patients intravenously. More particularly, the present invention pertains to an intravenous solution delivery system having a self-priming drip chamber. The present invention is also directed to an intravenous delivery system having a venting end cap to allow air present in an intravenous line to be removed.
2. Description of the Related Art
Medical liquid delivery systems are used by medical personnel to inject nutrients and/or medication into a patient's body. “Medical liquid delivery systems,” as used herein, include, for example, any system for delivering an intravenous solution such as glucose, saline solution, medical dyes, and medication in liquid form, to a patient. Such systems are used during surgery or when a patient is otherwise unable to ingest nutrients or medication orally.
Intravenous liquid delivery systems (“IV systems”), for example, generally include a bottle, bag or other container of intravenous liquid that is connected by a piercing assembly or “spike” through a series of conduits to a needle or cannula inserted into a vein in the patient. The bag or container is hung from a support at a higher elevation than the patient so that intravenous solution, such as liquid medicament flows through the conduits by the force of gravity. The piercing assembly provides liquid drawn out from the container to a drip chamber directly connected to the spike assembly. As a result, the drip chamber is positioned at a height above the patient. The drip chamber is made of a transparent or translucent material so that the “drip” (i.e. the solution flow rate into the drip chamber) can be visually inspected by medical personnel monitored by an electronic drop counter.
One or more valves are disposed within the system to control the intravenous liquid flow rate in the conduit connected to the patient. Knowing the drip rate and the size of each drop, the flow rate of the infused solution can be calculated. The IV system is connected to the patient and then the flow rate is set by adjusting the valve(s).
The drip chamber is constructed of a flexible material which forms a cylindrical chamber having a top inlet port directly connected to the spike assembly, and a bottom outlet port connected to the conduit leading to the needle, i.e. “the patient line”. A flow controller such as a roller clamp mounted to the outlet port conduit is used to adjust or throttle the liquid flow in the patient line by constricting or opening the outlet port conduit to adjust the flow rate. The inlet and outlet ports enclose opposite ends of a generally-cylindrical column of the drip chamber, and medicament drips from the inlet downwardly through the column where it collects at the bottom of the column and exits via the outlet.
If an infusion pump is used instead of a drip chamber, the infusion pump directly controls the IV-solution flow rate. If a drip chamber is used, however, the drip chamber must be “primed”. This typically involves allowing the drip chamber to be filled to a certain level to form a reservoir, e.g., ⅓ of the drip chamber volume, with the remaining ⅔ of the volume used to visually inspect the flow rate so that the number of drops can be counted over a period of time. In certain existing drip chambers, a “fill line” is provided on the drip chamber wall to visually indicate a level corresponding to the desired ⅓ volume amount. To allow the drip chamber to fill to the desired level, the roller clamp is closed off and the drip chamber is compressed by manually squeezing the chamber to remove air therefrom. The creation of a vacuum in the drip chamber as the walls return to a non-compressed state causes medicament to be drawn into the chamber from the medicament container.
One problem with such a priming technique is that if the drip chamber is squeezed too hard such that an excessive amount of air is removed, the reduced volume will be filled by an excess amount of medicament. In that case, the drip chamber will need to be emptied so that a visual drip region can be established for counting the drops of IV-solution. The emptying of the drip chamber takes additional time and may increase the risk of line contamination that may result in a nosocomial infection to the patient. This task is typically performed by disconnecting the medicament container from the drip chamber and then opening the roller clamp to allow the liquid in the drip chamber to drain through the patient line. This task is further complicated as a result of the direct connection between the drip chamber and the spike assembly. Such direct connection provides little or no maneuverability of the drip chamber because such manipulation may cause a disturbance of the connection between the spike assembly and the medicament container. On the other hand, if the drip chamber is squeezed too delicately so that not enough air is expelled, and consequently, only a small amount of liquid fills the drip chamber to form the reservoir, the drip chamber will need to be compressed a second (and perhaps even a third) time until the reservoir reaches an acceptable level.
Another problem with existing IV systems is that when the drip chamber is squeezed to adjust the solution flow rate, the pressurized conditions in the drip chamber cause the infused liquid to flow as a narrow stream into the drip chamber at a high velocity. As the high velocity liquid stream impinges the reservoir surface, bubbles are entrapped in the reservoir, thus causing an air-bubble mixture to form. When this occurs, a time-consuming task must be performed to purge the air bubbles from the drip chamber and from the conduit leading to the patient. This typically involves gently tapping the drip chamber and the conduit leading to the patient. If air bubbles are not purged, they may enter the patient and cause an embolism or other harmful effects. Unwanted air bubbles may also be formed from a rapid filling of IV-solution into the conduit leading to the patient in infusion pump systems (e.g., when no drip chamber is present). Such air bubbles are formed on the inside surface of the conduit and are typically removed by gently tapping the conduit.
These drawbacks reduce the efficiency in which IV systems can be connected to patients when, especially in emergency conditions, time may be of the essence. Efficiency is also important to reduce the time spent by health care professionals in setting up such IV systems, thereby according such professionals more time to tend to other patients or perform other tasks.